A method for manipulating a nucleoside includes converting guanosine to 5- methyluridine by means of biocatalytic transglycosylation. The biocatalyst comprises a combination of a purine nucleoside phosphorylase from Bacillus halodurans, PNPase (BH1531 ) of sequence ID No 1, or a protein with at least 90% sequence similarity thereto, and a pyhmidine nucleoside phosphorylase (PyNPase).
